queue

This is the class of queue objects. Queues are conceptually (but not
necessarily implementationally) like first-in first-out lists, with
objects being enqueued by being appended onto the end and dequeued by
being popped off the front. Queues are more convenient than lists in a
multiprocessing environment because enqueuing and dequeuing operations
are atomic (they will complete without a process switch) and because
dequeuing has a built-in wait capability. Queues have no intrinsic
size limit.

Queues are created with make-instance. The following form will
return a new queue: